Imagine that you lived in a house with a relatively private backyard: fences on all three sides, trees around the perimeter, and no easy way for the neighbors to peek in. Say you’re out there playing with your kids, or sunbathing, or consummating a romantic encounter in a hot tub that, let’s be honest, you rarely use. If I, intrepid journalist, were to appear overhead in a helicopter with the specific intent of peering down onto your property, you’d be justified in thinking that I violated your reasonable expectations of privacy. But your common-sense notions would be at odds with America’s mixed-up Fourth Amendment jurisprudence. "In the 1989 case Florida v. Riley, the U.S. Supreme Court ruled that since airplanes and helicopters often fly over private property, citizens do not have a reasonable expectation of privacy that their activities will not be observed from the air," Ronald Bailey explains in Reason. "Consequently, the police were permitted use of evidence obtained without a search warrant from helicopter observation of a greenhouse in which they suspected marijuana was being grown." At the time, aerial surveillance was at least constrained in practice by the significant cost of flying a helicopter. But today, at the dawn of the cheap-drone era, precedents like the one set in 1989 pose an novel threat to privacy rights. Hence the effort by California lawmakers to pass added protections into law: Earlier this month the California State Assembly voted to require police to obtain warrants to use drones for surveillance except in exigent circumstances. Now the State Senate has handily passed the legislation with a 25 to 8 vote. If Governor Jerry Brown signs this law when it crosses his desk, the Golden State will have struck the right balance: permitting drone surveillance in cases where police obtain an individualized warrant, while insisting on privacy rights consistent with the original understanding of the Fourth Amendment, not the diminished version that War on Drugs jurisprudence has given us. Reuters reports there is opposition to the bill from the public-employee unions that represent law enforcement, as well as the Los Angeles District Attorney’s office, which calls the law "an inappropriate attempt to impose search and seizure requirements on California law enforcement agencies beyond what is required by the 4th Amendment." Without conceding that this law goes beyond the Fourth Amendment, the district attorney’s argument is notably at odds with the notion that the Bill of Rights was a partial, incomplete articulation of the minimum rights owed a free people, not an upper bound on protecting liberty. Privacy-loving residents of other states should urge their legislators to follow suit.